Slip for oil well tools



June 18, 1940. c, BURT a 2,204,659

SLIP FOR OIL WELL TOOLS Filed Dec. 25, 19:59

CLARENCE BUR?) ar comm Patented June .18, 1940 UNlIED STATES 2,204,659smr i on on. WELL TOOLS Clarence E.,Burt, LosAngeles, CaliL, assignor toBaker Oil Tools, Inc., Huntington Park, Calif" a corporation ofCalifornia Application December'23, 1939, Serial No. 310,809

9 Claims.

This invention relates to slips, being particularly concerned with slipsdesigned for use as component parts of oil well tools.

Slips are usually provided with wickers or teeth which bite or dig intocasing or tubing to couple or anchor oil well tools thereto. In someapplications, the slips irretrievably anchor oil well tools to thecasing, and if it is later desired to remove the tool, this isaccomplished by drilling to break it into pieces, preferably smallenough to be removed from the casing by the drilling fluid. Heretoforeit has been difficult to drill up the slips because of their heavysection, despite the use of frangible material such as cast 5 iron. Thepresent invention is accordinglyconcerned with slip constructionscapable of being broken up more readily by a drilling bit.

It is usual practice to form slips with a generally conical or.frusto-conical surface, so that upon moving relatively to a companionconical or frusto-conical expander, they will be shifted radially intoanchoring engagement with a cooperable member, as the walls of a casing.Because of the divergent surface of a cone or conoid its radius ofcurvature correspondingly increases. As

a consequence, should the inner cone-contacting surface of a cooperableslip be formed with a radius of curvature equal to that of the smallerend of the cone, to provide a surface contact,

30 therebetween, upon being positioned at the larger end of the cone thesurface contact will be lost due to the different radii of curvatures ofthe inner slip surface and the larger diameter cone surface. The slipwill then have only a two- 35 point or line contact with the cone.Should the inner surface of the casing have a larger radius of curvaturethan the wickers on the slips, the slips will only make point orlongitudinal line contact with the casing, the anchoring efiect be- 40ing concentrated at the line contact region, and the other wickerportions remaining vineilfective for anchoring purposes.

In my Patent No. 2,153,035, Method of producing slips for oil welltools, the difiiculty noted 45 has been overcome to a certain extent byproviding a weakened longitudinal section in each slip segment so thateach initial segment will be broken into two sections by the wedging andclamping action of the cooperable cone and cas- 50 mg, and therebyengage both of these parts over a greater area and with greatersecurity. While this arrangement ofiers advantages, each part of theslip is still of too great a Size to be drilled up or removed with easeand rapidity. It is, 5 therefore, a further. object of this invention toprovide a slip which will be broken up into relatively small pieces uponbeing expanded into engagement with a well casing, these piecesthereafter requiring very little if any action by the drilling bit toeffect their removal from the casa ing by the drilling fluid.

This invention has other objects that will become apparent from aconsideration of the embodiment shown in the drawing accompanying andforming part of the present specification. This form will now bedescribed in detail, but it is to be understood that such detaileddescription is not to be taken in a limited sense, since the scope ofthe invention is best defined by the appended claims. l5

Referring to the drawing:

Figure 1 is a perspective view of the slips mounted on a packer body,prior to their expansion into engagement with a well casing;

Figure 2 is a view similar to Figure 1 with the slips expanded intogripping engagement with the casings and Figure 3 is an enlargedperspective view of one of the arcuate slip segments.

One specific slip A embodying the present invention is shown in thedrawing as forming part of a wellpacker B adapted to be anchored to thecasing C by the segmental slips A, which are initially secured to theconical expander D of the packer by shear screws E. The inner surface Inof each slip is tapered to cooperate with the companion and opposedtapered surface ll of the cone, so that upon relative movement occurringbetween the slips and cone the former will be urged radially outwardlyuntil their wickers I2 are firmly embedded in the casing. By beingwedged between the cone and casing, the slips serve to anchor the wellpacker in the desired position within the casing.

Each slip is formed with a plurality of longitudinal grooves I3 on itsinner periphery, defined by the separating longitudinal ribs it. Thesegrooves extend substantially along the entire length of the slip, butare of variable depth due to the cone-contacting, tapered inner face Illof 45.

the slip. That is, each groove I3 is deeper at the largercross-sectional end of the slip, its bottom wall 13a merging into theinner peripheral surface l0 atthe smaller end. In the instant case, thiseffect is produced by casting or otherwise forming its groove with itsbottom l3w generally parallel to the outer face of the slips. At thosepoints where the shear screws E initially secure the slips to the coneor body of the packer,.the longitudinal ribs H are interconnected by abridge l5 through which a hole l6 for a screw is provided. This designis required by the necessity for producing a shearing action on thescrews, for were the screws to extend through one of the grooves l3 itwould be subjected to a bending action rather than a pure shearingaction.

As aforementioned, upon sliding'on the cone toward casing engagingposition, the radius of curvature of any section of the inner surface Inof each slip is less than that of the cone surface II with which itcontacts. After contacting the casing, localized thrust loads will beimposed on each slip segment at the initial wedging points or lines ofcontact with the cone and casing, introducing lateral bending moments,whose attendant thrusts and leverages will break each slip at eachsection through the longitudinal grooves l3, not only producing a betterand more uniform gripping or anchoring of the wickers l2 in the casing,but also providing a greater surface of contact between the slip piecesand the cone.

While the desirable smaller slip segments result from the longitudinalgrooves l3, it has been found that these pieces are still too large,rendering it difficult to drill up or disintegrate the well packer afterit has been set in the casing. It is accordingly proposed to provideadditional weakened sections, such as result from spaced outercircumferential weakening grooves I! on each slip, which can be eithercast, machined, or otherwise formed therein. These grooves preferably donot diminish the number of wickers If! on the slips, being definedbetween adjacent wickers and only necessitating the removal or omissionof non-casing engaging wicker portions. It is to be noted further thatthe circumferential grooves are of varying depth, those at the thickerportion of the slip being deeper than those at the narrower portion.This is done to provide substantially the same weakening effect atdifferent portions of the slips. Furthermore, the circumferentialgrooves I! may or may not intersect the longitudinal grooves l3,depending solely on the depth to which they are carried. Shouldintersection of the grooves occur, no detrimental effects would resultsince the slip sections defining the circumferential grooves would stillbe connected through the agency of the ribs H defining the longitudinalgrooves.

The cooperative weakening effects of the longitudinal andcircumferential grooves cause each slip to be broken up into relativelysmall pieces upon being wedged between the casing and cone,

these pieces remaining in wedged position and anchoring the well tool tothe casing. Assuming that five longitudinal grooves l3 are formed in theinner face of the slip and two circumferential grooves on the outerface, each slip will be broken into eighteen pieces by being fracturedthrough the groove sections. It is to be understood however that thenumbers mentioned are solely for illustrative purposes and should not beconstrued as conferring any limitations upon the invention.

The small pieces are of such dimensions as to be removed upwardly by thedrilling fluid away from the well packer B, and thereby do not impedethe progress of the drilling bit in removing or disintegrating thepacker. However, should each slip segment fail to fracture into thenumber of pieces defined by the weakening grooves, the action of thedrilling bit will readily break the slip at least into such number ofpieces, so that in any event and irrespective of the breaking action ofthe slips upon being set in the casing, re-

accepts movalof the slips under the action of the drilling bit will beexpedited.

While the slip has been disclosed with the circumferential grooves I! atright an les to the longitudinal grooves l3, the circumferential groovesor longitudinalgrooves can be inclined somewhat if desired and stillproduce the same weakening effect. Furthermore, all of the grooves couldbe provided on only one slip face, if desired; or their positionsinterchanged from the specific example disclosed.

I claim:

1. A slip for well tools having wickers on one face thereof and atapered surface on another of its faces, said tapered face beingprovided with a plurality of spaced generally longitudinal grooves, andsaid wickered face being provided with a plurality of spacedcircumferential grooves of a depth greater than that of said wickers.

2. A slip for well tools having wickers on one face thereof and atapered surface on an opposed face thereof, said tapered face beingprovided with at least one generally longitudinal groove, and saidwickered face being provided with at least one circumferential groove ofa depth greater than that of said wickers.

3. A slip for well tools having wickers on one face thereof and atapered surface on an opposed face thereof, one of said faces beingprovided with at least one generally longitudinal groove, and the otherface being provided with at least one circumferential groove in additionto the grooves defined by said wickers.

4. A slip for-well tools having wickers on an outer face thereof and atapered surface on an inner face thereof inclined to said outer face todefine a longitudinal slip cross-section decreasing in width from oneend to the other, one of said faces being provided with at least onegenerally longitudinal groove increasing in depth toward the wider slipsection, and the other face being provided with at least onecircumferential groove in addition to said grooves defined by saidwickers.

5. A slip for well tools having wickers on an outer cylindrical facethereof and a frusto-conical surface on an inner face thereof, one ofsaid faces being provided with at least one generally longitudinalgroove increasing in depth toward a wider slip section, and the otherface being provided with a plurality of spaced circumferential grooves,one of said circumferential grooves at a wider slip section being deeperthan another circumferential groove at a narrower slip section. a

6. A slip for well tools having wickers on an outer cylindrical facethereof and a frusto-conical surface on an inner face thereof, saidinner face being provided with a plurality of spaced generallylongitudinal grooves each increasing in depth toward a wider slipsection, said other face being provided with a plurality of spacedcircumferential grooves, one of said circumferential grooves at a widerslip section being deeper than an adjacent circumferential groove at anarrower slip section.

7. A slip for well tools having wickers on an outer cylindrical facethereof and a frusto-conical surface on an inner face thereof, said sliphaving a plurality of spaced generally longitudinal Weakened sectionsand spaced circumferential weakened sections, to cause said slip tobreak into small pieces.

8. A slip for well tools having wickers on an outer cylindrical facethereof and a frusto-conical surface on an inner face thereof, said slipbeing provided with a plurality of spaced grooves lying in generallyparallel planes and another group of spaced grooves lying in generallyparallel planes at an angle to said first-mentioned planes, said groovesbeing of a depth and extent to produce many weakened sections in saidslip along which it may be broken into a large number of small pieceswhile in a well casing.

9. An annular slip segment for well tools whose wall increases inthickness in one direction of its axis, said wall having a plurality ofspaced grooves lying in generally parallel planes and another group ofspaced grooves lying in generally parallel planes at an angle to saidfirst-mentioned planes, said grooves extending into said wall to anextent producing many weakened sections therein along which said slipscan be readily broken into a large number of small pieces while in awell.

CLARENCE E. BURT.

